The WSN specification status that when sending a RegisterPublisher message, the element PublisherReference may be null when Demand is false.
"This component MUST appear if the /wsn-br:RegisterPublisher/Demand component has value "true". If this component is missing, the Publisher is either not a Web service, or does not wish to receive messages from the NotificationBroker."
The WSN Broker included with the release throws a fault when sending a null PublisherReference
rPublisher has thrown exception, unwinding now: org.oasis_open.docs.wsn.brw_2.PublisherRegistrationFailedFault: Invalid